Method of making tin tetrachloride



AWM! 3011935. 1 BURGESS HWgyw@ METHOD OF MAKIG TIN TETRACHLORIDE Filed July 27, 1,932

Il lil' INVENTOR QW @My/M" Patented Apr. 30, 1935 PATENT OFFICE 1,999,179 METHOD F VIWAKING TIN TETRACHLORIDE Louis Burgess, New York, N. Y., assigner to William P. Alexander, Ridgewood, N. J.

Application July 27, 1932, Serial No. 625,169

7 Claims.

The invention will be fully understood from the following description read in conjunction with the drawing, in which,

Fig. l is a vertical section through apparatus in which-the invention may be carried into effect, and

Fig. 2 is a horizontal section through Fig. 1 on the plane indicated by I-I.

' I designates a reaction tower comprising the outer shell 2, which may for example be formed Vof steel, and is preferably provided with the refractory liner 3. The tower I is adapted to hold a pool 4 of molten tin in the lower part thereof. Provision is made for the continuous introduction of chlorine under pressure to this pool beneath the surface thereof and adjacent the baselof the tower I. Such provision comprises the tank I 0, which may for example be a tank car body adapted to transport liquid chlorine. The tank is controlled by the valve II, connected through the pipe I2 to the distributor I3, which discharges adjacent the base of the tower I. The tower is also provided with a series 2li of horizontal trays 2| to 26 inc. These trays may be formed of refractory material bonded into the refractory liner 3. The trays do not entirely'span the tower, but terminate a short distance before reaching the opposite wall, thereby forming a series of staggered openings 30, 3|, 32, 33, 34 and 35. These openings, in combination with the tower, form a tortuous path so that gas passing upwardly through the tower passes horizontally over the surface of the trays. It will of course be understood that the trays could alternatively span the entire tower and carry within themselves staggered openings vertically disposed, adapted to perform the same function. Suitable provision` is also made for the introduction of liquid tin adjacent the upper part of the tower. This comprises'the melting pot 4t, surrounded by the refractory setting 4I, heated'by the' burner 32. Products of combustion escape through the stack 43. discharges through the trap 44 and pipe 45, controlled by valve 46, onto the surface of the uppermost tray 2i. In charging the apparatus, sufficient liquid tin is introduced to llall of the trays and in addition to form a pool of substantial depth in the base of the tower I, which may for example overlay the outlet It for a distance of from one to three feet at the commencement of operations. Products of the reaction escape from the tower through the outlet 5U which is connected into the mid-section of the tower 5I. The tower 5| carries cooling coil The pot All 52 adjacent the top thereof and heater coil 53 adjacent the bottom thereof. The tower 5I is spanned by the grate v54, and before` operation a number of small ingots of tin are passed in through the manhole to form a mass 56 of divided solid tin resting on the grate 54 up through which the reaction products pass.

In operation, the tower I is charged with liquid tin, as aforesaid, and a continuous supply of chlorine is passed in by manipulation of Valve i i.

This bubbles up through the liquid tin in the base lo of the tower, thereby forming a reaction mixture which may contain tin dichloride, tin tetrachloride and chlorine. If operations are commenced with a relatively thick'layer of tin overlaying the outlet Ill, tin dichloride. appears to predominate; 15

and as the layer of tin becomes of diminished thickness, the Vreaction products consist principally of tin dichloride with a minor proportion of chlorine. The chlorine and tin tetrachloride are normally gaseous at the temperatures involved, and tin dichloride will usually have sufficient vapor pressure to pass in part upwardly in the gas. Some of the tin dichloride will separate out in liquid or semi-liquid form as a layer 5 iioat- 25 ing on the surface of the pool fl. Where the tin dichloride is present as a component of the gas, it will deposit on the upper surface of the trays 2l to 26 inc.

I am aware that tin tetrachloride has been 30 heretofore made by passing chlorine over the surface of liquid tin, and, alternatively, by passing chlorine through liquid tin. Both these methods have, however, certain limitations, and the new method herein described has specic advantages 35 not possessed by either of the older methods. For example, in making tin tetrachloride by passing chlorine through molten tin, a very compact apparatus of small dimensions may be used,

but the reaction is not ordinarily complete in the 40 desired direction. Unless the temperature of operation and depth of metal are carefully controlled, the reaction either runs to the production of tin dichloride or to the production of tin tetrachloride with unreacted chlorine. of the liquidV tin is lowered, the proportion of chlorine tends to increase and this of course results in an increased proportion of chlorine in the tin tetrachloride recovered from the system.

As the level 45 In accordance with my process, the gas pro- 50 duced by passing chlorine through the liquid tin in the pool 4 is then passed in succession over the surface of the liquid tin laying on the trays 2i to 26. During the early stages of the reaction, 55

and/or where the conditions are so adjusted as to produce tin dichloride, this deposits and overlays the molten tin carried by the trays. During the latter stages of the reaction, products coming from the base of the tower contain free chlorine. This chlorine will react with the tin dichloride which overlays the molten tin on the trays. If. the tin dichloride is not present or has become exhausted, the chlorine will react directly with the molten tin itself. Furthermore, inasmuch'as the chlorine principally attacks the molr ten tin in the pool Il, the tin laying on the trays 2l to 2G will not be heavilyattackediuntili` the tin in the pool has become at least. partially exhausted, and for this reason the tin laying on thetrays presents a substantially uniform reactive surface during the entire period of operation;v While oi" course charging of molten tin may be continu,- ously effected, Iiind it somewhat more convenient to do so intermittently, relying; upon the tinv carried bythe trays to maintain the system atv a point of' high eiciency during the entire cycle.

In practice, the trays; andtheir contents, as well as the gasy mixture passing over the same,

will ordinarily beat a temperature of from 235- to Llilo" C.; whereas the liquid tinin the pool owing to the heat generatedby.v the reaction, may be at a temperaturev of from 300 to 700 C. and will ordinarily be at a temperature. of. from 300 to 500 C.

lIhe gas passing from thesystem through the outlet will normally consist almost exclusively of tin tetrachloride and may contain a smallproportion of chlorinefwhich is not desirable in thel finished product. It is of ccursepossible to pass this gas over solid tin with the result of' at least partially reacting the chlorine and the tin. This is somewhat complicated by thev diluent effect of i the tin tetrachloride and by the solvent effect of liquid tin tetrachloride if condensation is simultaneously attempted.

In my apparatus the gas passes upwardly in the tower 5I through the mass 56 of solid divided tin. In the upper part of the tower, tin tetrachloride is continuously condensed by means of water passing throughthe coil 52', sov thatV the tin tetrachloride flows downwardly over the solid divided tin in counter current contact to the'gas. Inasmuch as the tin tetrachloride iscontinuously condensed, it does not carry the chlorineVv out of the system, and the gas passing oif through the pipe 5l, controlled by valve E8; is merely the small proportion of unreactive gas which may, for example, be air present inthe apparatus on starting up. Thekv condensed tin tetrachloride flows downwardly into the base 59r of the tower 5 I. The chlorine is principally driven out of the condensate by the heat of the gas coming in` through the pipe 50. If under the operating conditions this heat is not sufcient to'entirely drive out the chlorine, or to eliminatethe tendency of the tin tetrachloride -to dissolve fresh chlorine out ofthe gas, use is made of the heater coil` 53. Thismay, for example, be supplied with steam under pressure sufficient to boil the tin tetrachloride in the base 5s of the tower 5l, thereby driving oi every trace of chlorine contained therein. This chlorine, together with the small amount of tin tetrachloride vaporized, passes upwardly in the tower 5l so that the chlorine is continuously forced into contact with the mass 56 of divided tin until complete reaction has occurred.. Any excess of tin tetrachloride over that necessarytomaintain the pool 59 in the base of the tower 5l is Withdrawn through the overflow pipe 60 controlled by the valve 6l.

The foregoing description is for purposes of illustration and not of limitation, and it is therefore my intention that the invention be limited only by the appended claims or their equivalents, wherein I have endeavored to claimbroadly all inherent novelty. f

l. Process of generating tin tetrachloride, which comprises passing chlorine upwardly through a first body of molten tin, thereby producing a gas'containing tin chloride and chlorine, thereafter passing said gas in a generally horizontal' direction over the surface of a body of molten tin` separate and independent from said first body, andthereafter conducting away the said gas and condensing the tin tetrachloride contained therein.

2. Process of generating tin n tetrachloride,

which comprisespassing chlorine upwardly Y through a first body of molten tin, thereby pro ducing a gascontaining tin. chloride andchlorine, thereafter passing said gasY in argenerallyhori l zontal direction over the surface of a bodyof, molten tin separate and independent from said rst body while maintaininga temperature of not. exceeding 400 C., and thereafter conducting away the said gas and condensing the tin-tetrachloridecontained therein.

3. Process of generating tin* tetrachloride, whichY comprises passing chlorineY upwardly through molten tin, thereby producing a gas containing tin chloride and chlorine, thereafter'passing said gas over the surface of molten tin,there after passing said gas over-the surfacefofsolid. tin, and condensing and recovering the tin tetra,- chloride contained therein. l Y

`4. Process of generating tin tetrachloride; which comprises passing chlorine upwardly through molten tin, thereby producing a gas containingY tin chloride and chlorine, thereafter passing said gas over the surface of molten tin while maintaining a temperature of not exceeding 400 C., thereafter passing said gas over the surface ofr solid tin, and condensing and recovering the tin tetrachloride contained therein.

5. Process of making tin tetrachloride, which drawing. said gas, passing said' gas upwardly through afmass ofdividedsolid tin, continuously condensing tin tetrachloride adjacent the upper part of said mass, collecting condensed tin chloride adjacent the lower part of said mass, heating the said condensed tin chloride to a temperature sufficient to substantially free it of dissolved chlorine, and returning the chlorine thereby evolved to the said mass.

7. Process of making tin tetrachloride, which comprises forming a pool of liquid tin, forming a vertical series of layers of liquidtin above the said pool, said layers and pool being so arranged that an excess of molten tin supplied to any layer would overflow into the next succeeding lower thereafter conducting away said gas and conlayer and an excess of molten tin supplied to the densing the tin tetrachloride contained therein,

lowest layer would overflow into said pool, conand intermittently replenishing the tin in said tinuously passing chlorine into said pool, therelayers and pool by introducing molten tin adja- 5 by forming a gas containing tin tetrachloride and cent the upper part of said series.

chlorine, passing said gas in a general upwardly direction over the surface of the said layers, LOUIS BURGESS. 

